1. Field of the Invention
The invention relates to position control means and a method to control the speed pattern of servo motors by exponential deceleration and acceleration. Particularly, even if the speed pattern of a servo motor is expressed as the exponential function, the invention relates to position control means and a method which decide destination position at every sampling time by calculating a linear equation forming an exponential function curve instead of calculating a complicated exponential function.
2. Related Art
Conventionally, when the speed of a servo motor is exponentially controlled in a position control system, (as shown generally in FIG. 2), in acceleration, the speed of a motor v(t) is: EQU v(t)=Vmax * {1-exp(-t/.tau.)}
and, at every sampling time, the speed of a motor is: EQU v(Ts)=Vmax * {1-exp(-Ts/.tau.)}
The destination position at a sampling time T.sub.s is produced by the equation: EQU S(Ts)=v(Ts) * Ts =Vmax * {1-exp(-Ts/.tau.)}* Ts.
In a deceleration interval, the speed of a servo motor is: EQU v(t)=Vmax * exp(-t/.tau.)
and at every sampling time Ts, the speed of a servo motor, v(Ts) is: EQU v(Ts)=Vmax * exp(-Ts/.tau.).
At every sampling time T.sub.s, the destination position is: EQU S(Ts)=v(Ts) * Ts =Vmax * exp (-Ts/.tau.) * Ts.
Hence, the arithmetic time is relatively long. This creates defects in the control system of the servo motor, resulting in unsafe servo control.